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United States Patent | 5,325,495 |
McLellan | June 28, 1994 |
A pipelined computer system employs a queue stage to receive the output of one pipeline stage when a stall occurs in the next stage or downstream of the next stage. This avoids stalling earlier stages of the pipeline. Subsequently, the pipeline advances through the queue, until a bubble occurs. When a bubble is subsequently generated upstream and enters the queue stage, a multiplexer switches the input of the next stage to receive the output of the one stage instead of from the queue stage, and the content of the queue is overwritten. By this mechanism, the delays inherent in processing branches can be reduced.
Inventors: | McLellan; Edward J. (Milford, MA) |
Assignee: | Digital Equipment Corporation (Maynard, MA) |
Appl. No.: | 103815 |
Filed: | August 9, 1993 |
Current U.S. Class: | 712/219; 712/229 |
Intern'l Class: | G06F 009/38 |
Field of Search: | 364/DIG. 1 MS File,DIG. 2 MS File 395/375,800 |
4777594 | Oct., 1988 | Jones et al. | 364/200. |
4974154 | Nov., 1990 | Matsuo | 395/375. |
5019967 | May., 1991 | Wheeler et al. | 395/775. |
Troiani et al, "The VAX 8600 I Box, A Pipelined Implementation of the VAX Architecture", Digital Technical Journal, Aug. 1985, pp. 24-42. Kane, "MIPS R2000 RISC Architecture", Prentice Hall, 1987, pp. 1-1 to 1-14, 2-1 to 2-5, 2-12 to 2-13, 3-13 to 3-16. Smith, "A Study of Branch Prediction Strategies", 8th Annual Symposium on Computer Architecture, May 12-14, 1981, pp. 135-148. Bakoglu et al., "The IBM RISC System/6000 processor: Hardware Overview", IBM J. Res. Develop., Jan. 1990, pp. 12-22. Oehler et al, "IBM RISC System/6000 processor architecture", IBM J. Res. Develop., Jan. 1990, pp. 23-36. Grohoski, "Machine Organization of the IBM RISC System/6000 processor", IBM J. Res. Develop., Jan. 1990, pp. 37-58. Losq, "Generalized History Table for Branch Prediction", IBM Tech. Discl. Bulletin, Jun. 1982, pp. 99-101. Rao, "Techniques for Minimizing Branch Delay . . .", IBM Tech. Discl. Bulletin, Jun. 1982, pp. 97-98. |